The
driver provides a convenient means for user applications to manipulate the
state of the parallel port, enabling easy low-speed I/O operations without
the security problems inherent with the use of the
/dev/io
interface.
PROGRAMMING INTERFACE
All I/O on the
interface is performed using
ioctl ();
calls.
Each command takes a single
u_int8_t
argument, transferring one byte of data.
The following commands are available:
PPIGDATA , PPISDATA
Get and set the contents of the data register.
PPIGSTATUS , PPISSTATUS
Get and set the contents of the status register.
PPIGCTRL , PPISCTRL
Get and set the contents of the control register.
The following defines correspond to bits in this register.
Setting a bit in the control register drives the corresponding output low.
STROBE
AUTOFEED
nINIT
SELECTIN
PCD
PPIGEPP , PPISEPP
Get and set the contents of the EPP control register.
PPIGECR , PPISECR
Get and set the contents of the ECP control register.
PPIGFIFO , PPISFIFO
Read and write the ECP FIFO (8-bit operations only).
EXAMPLES
To present the value 0x5a to the data port, drive STROBE low and then high
again, the following code fragment can be used:
int fd;
u_int8_t val;
val = 0x5a;
ioctl(fd, PPISDATA, &val);
ioctl(fd, PPIGCTRL, &val);
val |= STROBE;
ioctl(fd, PPISCTRL, &val);
val &= ~STROBE;
ioctl(fd, PPISCTRL, &val);
BUGS
The inverse sense of signals is confusing.
The
ioctl ();
interface is slow, and there is no way (yet) to chain multiple operations together.
The headers required for user applications are not installed as part of the
standard system.
